From 0a8e7b7d08466b5fc52f8e96070acc116d82a8bb Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Wed, 15 Apr 2020 17:36:22 -0400 Subject: SUNRPC: Revert 241b1f419f0e ("SUNRPC: Remove xdr_buf_trim()") I've noticed that when krb5i or krb5p security is in use, retransmitted requests are missing the server's duplicate reply cache. The computed checksum on the retransmitted request does not match the cached checksum, resulting in the server performing the retransmitted request again instead of returning the cached reply. The assumptions made when removing xdr_buf_trim() were not correct. In the send paths, the upper layer has already set the segment lengths correctly, and shorting the buffer's content is simply a matter of reducing buf->len. xdr_buf_trim() is the right answer in the receive/unwrap path on both the client and the server. The buffer segment lengths have to be shortened one-by-one. On the server side in particular, head.iov_len needs to be updated correctly to enable nfsd_cache_csum() to work correctly. The simple buf->len computation doesn't do that, and that results in checksumming stale data in the buffer. The problem isn't noticed until there's significant instability of the RPC transport. At that point, the reliability of retransmit detection on the server becomes crucial. Fixes: 241b1f419f0e ("SUNRPC: Remove xdr_buf_trim()") Signed-off-by: Chuck Lever --- net/sunrpc/auth_gss/gss_krb5_wrap.c | 7 +++---- net/sunrpc/auth_gss/svcauth_gss.c | 2 +- net/sunrpc/xdr.c | 41 +++++++++++++++++++++++++++++++++++++ 3 files changed, 45 insertions(+), 5 deletions(-) (limited to 'net/sunrpc') diff --git a/net/sunrpc/auth_gss/gss_krb5_wrap.c b/net/sunrpc/auth_gss/gss_krb5_wrap.c index 4905652e7567..cf0fd170ac18 100644 --- a/net/sunrpc/auth_gss/gss_krb5_wrap.c +++ b/net/sunrpc/auth_gss/gss_krb5_wrap.c @@ -580,15 +580,14 @@ gss_unwrap_kerberos_v2(struct krb5_ctx *kctx, int offset, int len, */ movelen = min_t(unsigned int, buf->head[0].iov_len, len); movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip; - if (offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen > - buf->head[0].iov_len) - return GSS_S_FAILURE; + BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen > + buf->head[0].iov_len); memmove(ptr, ptr + GSS_KRB5_TOK_HDR_LEN + headskip, movelen); buf->head[0].iov_len -= GSS_KRB5_TOK_HDR_LEN + headskip; buf->len = len - GSS_KRB5_TOK_HDR_LEN + headskip; /* Trim off the trailing "extra count" and checksum blob */ - buf->len -= ec + GSS_KRB5_TOK_HDR_LEN + tailskip; + xdr_buf_trim(buf, ec + GSS_KRB5_TOK_HDR_LEN + tailskip); *align = XDR_QUADLEN(GSS_KRB5_TOK_HDR_LEN + headskip); *slack = *align + XDR_QUADLEN(ec + GSS_KRB5_TOK_HDR_LEN + tailskip); diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c index d0a2f084e5a4..50d93c49ef1a 100644 --- a/net/sunrpc/auth_gss/svcauth_gss.c +++ b/net/sunrpc/auth_gss/svcauth_gss.c @@ -906,7 +906,7 @@ unwrap_integ_data(struct svc_rqst *rqstp, struct xdr_buf *buf, u32 seq, struct g if (svc_getnl(&buf->head[0]) != seq) goto out; /* trim off the mic and padding at the end before returning */ - buf->len -= 4 + round_up_to_quad(mic.len); + xdr_buf_trim(buf, round_up_to_quad(mic.len) + 4); stat = 0; out: kfree(mic.data); diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 15b58c5144f9..6f7d82fb1eb0 100644 --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -1150,6 +1150,47 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf, } EXPORT_SYMBOL_GPL(xdr_buf_subsegment); +/** + * xdr_buf_trim - lop at most "len" bytes off the end of "buf" + * @buf: buf to be trimmed + * @len: number of bytes to reduce "buf" by + * + * Trim an xdr_buf by the given number of bytes by fixing up the lengths. Note + * that it's possible that we'll trim less than that amount if the xdr_buf is + * too small, or if (for instance) it's all in the head and the parser has + * already read too far into it. + */ +void xdr_buf_trim(struct xdr_buf *buf, unsigned int len) +{ + size_t cur; + unsigned int trim = len; + + if (buf->tail[0].iov_len) { + cur = min_t(size_t, buf->tail[0].iov_len, trim); + buf->tail[0].iov_len -= cur; + trim -= cur; + if (!trim) + goto fix_len; + } + + if (buf->page_len) { + cur = min_t(unsigned int, buf->page_len, trim); + buf->page_len -= cur; + trim -= cur; + if (!trim) + goto fix_len; + } + + if (buf->head[0].iov_len) { + cur = min_t(size_t, buf->head[0].iov_len, trim); + buf->head[0].iov_len -= cur; + trim -= cur; + } +fix_len: + buf->len -= (len - trim); +} +EXPORT_SYMBOL_GPL(xdr_buf_trim); + static void __read_bytes_from_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigned int len) { unsigned int this_len; -- cgit v1.2.3